1. Field of the Invention
The present invention relates to a method and apparatus for controlling an electromagnetically operated engine valve, in which the engine valve is brought into an initial condition in advance of an engine startup wherein the engine valve is held in one of a closed position and a full open position.
Such an electromagnetically operated engine valve, i.e., intake and exhaust valves, is biased by a pair of springs to be held in a mid-open position between the closed and full open positions. The engine valve is moved to the closed or full open position against the biasing force of the spring by an electromagnetic attraction. The attraction is generated upon energizing one of two electromagnets and applied to the engine valve via an armature associated with the engine valve. The engine valve is forced to an initialized condition in which the engine valve is placed and held in the closed or full open position, in advance of an engine startup. This is referred to as an initialization control of the engine valve. After that, in the case of actuating the engine valve in the opening direction, the valve-closing electromagnet is de-energized to move the engine valve into the opening direction by the biasing force of the valve-opening spring. When the engine valve is moved closer to the valve-opening electromagnet, the valve-opening electromagnet is energized to attract the engine valve. The engine valve then is moved to and held in the full open position by the attraction of the valve-opening electromagnet. On the other hand, in the case of actuating the engine valve in the closing direction, the valve-opening electromagnet is de-energized to permit the engine valve to move in the closing direction and approach the valve-closing electromagnet. The valve-closing electromagnet is then energized to attract and hold the engine valve in the closed position.
The initialization control of the engine valve may be conducted in such a simple manner as to onetime energize the valve-opening or valve-closing electromagnet to thereby move the engine valve from the mid-open position to the closed or full open position with one stroke. However, in the simple initialization control, a stroke of the engine valve is relatively large. This causes an increased power consumption.
U.S. Pat. No. 4,614,170 attempts to reduce a power consumption by oscillating an engine valve with an increased amplitude using resonance phenomena of a spring/mass which occurs upon alternately energizing valve-opening and valve-closing electromagnets. As a result, the valve is placed and held in one of the closed and full open positions.
However, in the latter conventional technique, upon the initialization control at a low temperature, a lubricating oil with an increased viscosity tends to increase friction, causing a power consumption greater than that in the former conventional technique. This will also cause an increased power consumption of a vehicular battery before completion of the initialization, leading to failure of the initialization of the engine valve.
The present invention contemplates to eliminate the above-described disadvantages of the conventional techniques. Specifically, it is an object of the present invention to provide a method and apparatus for controlling an electromagnetically operated engine valve, in which an improved initialization control of the engine valve is conducted.
According to one aspect of the present invention, there is provided an apparatus for controlling an engine valve operated by an electromagnetic actuator, the engine valve having a closed position and a full open position, the electromagnetic actuator including springs cooperating to bias the engine valve toward a mid-open position between the closed and full open positions and two electromagnets attracting and moving the engine valve in the closed and full open positions against spring forces of the springs upon being energized, respectively, the apparatus comprising:
sensor means for sensing a parameter to be used in determining a viscosity of an engine lubricating oil; and
a controller programmed to determine the viscosity of an engine lubricating oil on the basis of the parameter sensed and execute either one of a resonant initialization preceding an engine startup, in which the engine valve is oscillated with an increasing amplitude to be moved from the mid-open position to one of the closed and full open positions and held therein by alternate energization of the electromagnets, and a one-shot initialization preceding the engine startup, in which the engine valve is moved from the mid-open position to one of the closed and full open positions and held therein with one stroke by onetime energization of one of the electromagnets, depending on the determined viscosity of an engine lubricating oil.
According to a further aspect of the present invention, there is provided an apparatus for controlling an engine valve operated by an electromagnetic actuator, the engine valve having a closed position and a full open position, the electromagnetic actuator including springs cooperating to bias the engine valve toward a mid-open position between the closed and full open positions and two electromagnets attracting and moving the engine valve in the closed and full open positions against spring forces of the springs upon being energized, respectively, the apparatus comprising:
a sensor detecting a parameter to be used in determining a viscosity of an engine lubricating oil and generating a signal indicative of the parameter detected; and
a controller, in response to the signal generated from the sensor, determining the viscosity of an engine lubricating oil, the controller selecting either one of a resonant initialization preceding an engine startup, in which the engine valve is oscillated with an increasing amplitude to be moved from the mid-open position to one of the closed and full open positions and held therein, and a one-shot initialization preceding the engine startup, in which the engine valve is moved from the mid-open position to one of the closed and full open positions and held therein with one stroke, depending on the determined viscosity of the engine lubricating oil, and the controller developing a first control command for alternately energizing the electromagnets for the resonant initialization and a second control command for onetime energizing one of the electromagnets for the one-shot initialization.
According to a still further aspect of the present invention, there is provided a method of controlling an engine valve operated by an electromagnetic actuator, the engine valve having a closed position and a full open position, the electromagnetic actuator including springs cooperating to bias the engine valve toward a mid-open position between the closed and full open positions and two electromagnets attracting and moving the engine valve in the closed and full open positions against spring forces of the springs upon being energized, respectively, the method comprising:
determining a viscosity of an engine lubricating oil;
selecting either one of a resonant initialization preceding an engine startup, in which the engine valve is oscillated with an increasing amplitude to be moved from the mid-open position to one of the closed and full open positions and held therein by alternately energizing the electromagnets, and a one-shot initialization preceding the engine startup, in which the engine valve is moved from the mid-open position to one of the closed and full open positions and held therein with one stroke by onetime energizing one of the electromagnets, depending on the determined viscosity of an engine lubricating oil; and
executing the selected one of the resonant initialization and the one-shot initialization.